Integrated driver for controlling stepper servos with third-order S-curve acceleration and close loop feedback. Like TinyG, but using servos. Someone years ago upgraded the steppers on their M2 to use servos and made a video of it doing traverses at ridiculous speeds, but he never did say what he was using. Also reminds me of the T-Bone 3D printer cape for the BeagleBone Black someone made, but that looks like a defunct project; I believe that project used Trinamic controllers.

Anyway, my hardware design chops are nowhere near good enough to attempt a 3D printer board, but maybe somebody here is good at that, has a lot of free time, and wants to work on the next generation of CNC motion control.... The only real difficulty I can foresee is making sure the acceleration curves on all axes are synchronized, and also coordinated with the extruder.